Rheostat having molded base



Dec. 28 1926.

F. BOLLER RHEIbSTAT HAVING MOLDED BASE Filed Oct. 14, 1922 m 3 AT 1 INVENTOR. dWa/YW B/QY/P/Q/V ATTORNEY Patented Dec. 28, 1926.

UNITED STATES 1,612,174 PATENT OFFICE.

FRANK ROLLER, OF MOUNT VERNON, NEW YORK, ASSIGNOR TO THE CUTLER-HAMMER MFG. 00., OF MEWAUTKEE, WISCONSIN, A. CORPORATION OF WISCONSIN.

BHEOSTA'I' HAVING MOLDED BASE.

Application :flledbetober 14, 1922. Serial No. 594,469.-

This invention relates .to improvements in devices having molded bases to support and definitely position thereon wire helices or the like. I

While not limited thereto the invention is particularly applicable to rheostats, potentiometers and similar instrumentalities employed in radio apparatus.

In such devices wire helices are commonly employed and it has heretofore been proposed to support such a helix on the peri-phany of a circular insulating base, the latter to be formed preferably of molded insulation and preferably with a peripheral groove to receive the helix. However great difficulty has been experienced in forming such a base at leastwit out resort to complicated dies and expensive methods.-

An object of the present invention is that of obviating the aforementioned difficulties and disadvantages in the roduction of devices having bases of the a oreindicated preferred type.

Another object is that of providing a molded insulating base, of the special character aforeindicated, having its parts so correlated and arranged as to enable production thereof by the methods and ap aratus ordinarily employed in production 0 simple 0 or unreticulated shapes.

Another, object is that of providing for more adequate securement of the helical or other element carried b such base.

Another object is t at of providing an improved device em loying such base and havin structural an functlonal advantages to be iereinafter described.

Other objects and advantages will appear as the description proceeds.

In the accompanying drawing, wherein is illustrated a rheostat embodying the invention;

' Figure 1 is a vertical sectional view thereof, certain parts, however, being shown in side elevation;

Fig. 2 is a similar view illustrating a dilixttlarent mode of assembling and mounting; w 1 e,

Figs. 3 and 4 are respectivel back and front side-views illustrating t e rheostat unmounted.

Referring to the drawing the same illustrates a rheostat comprising a helical resistor 9 stretched within a peripheral groove of an insulating base 10, the latter to be mounted upon a suitable panel 11 as by means of screws or bolts indicated at 12. A- contactor 13 having a portion to engage the turns of the resistor is fixed upon a rotatable shaft 14, the latter being journaledwithin and centrally of the base 10 to pro-- vide for angular movement of the contactor to engage the various turns of the resistor sequentially, said shaft being provided with the usualknob 15 and pointer 16.

The peripheral groove of the baselO for race tion of the element 9 is-formed by axia ly spaced projecting lips located upon opposite sides of said element when assembled, whereas in practice the oppositely located lips are interrupted at spaced antl staggered regions, whereby the residual portions of said lips comprises a plurality of spaced and axially staggered projections or tongues 17 and 18. The location of said tongues upon opposite sides of the resistor element serves to hold the latter positively against shifting axially of the base Whereas the staggered relation of said tongues enables molding of the base in an ordinary press and ready removal therefrom, notwithstanding the reticulated contour of the base in the directionof necessary application of the molding presure.

Further, if desired, the opposing surfaces of lips 17 and 18'may be made of undercut formation to surround the helix to practically any desired extent, thereby providing for more positive positioning and holding of the helix. v

The base 10 is further provided with suit- 'able openings 19 to receive the bolts 12 and also with countersunk openings located near the edge thereof to receive terminal screws '20 and 21. In practice one end of the resistor 9 is preferably clamped about terminal screw 21 for securement to the base 10 in electrical connection with said screw. The other end of said resistor is anchored to an adjacent portion of the base as by looping or hooking within a suitable opening slot or recess in the base substantially as shown at 22, the intermediate portion of the resistor being wrapped and stretched peripherally about the base and within the groove thereof as aforedescribed, whereby the spring action of the resistor serves to maintain the same permanently and positively located Within said groove Said base 10 is further provided with a no peripheral shoulders forming therebetween a peripheral groove toreceive and hold a central opening to receive the shaft 14, said opening being counterbored to receive a collar 23 to be fixed to said shaft as by means of the set screw illustrated. A second collar 21 is similarly clamped upon said shaft upon the opposite side of the base. The contactor 13 also preferably surrounds said shaft in the well known manner, saidcontactor preferably having parts to interfit with the collar 24 as illustrated for causing the former to move angularly with the shaft. A jumper 25 serves to connect the contactor 13 with terminal screw 20 in a-well known manner.

The foregoing construction and arrangement provides, as shown inFigs. 1 and 2, for mounting of the rheostat either in front or in rear of the support or panel 11, whereby great flexibility of application is provided. In assembling the rheostat in the relation shown in Fig. 2 the shaft 14 is first inserted backwardly through the support 11 and the collar 23 is fixed thereon in suitable relation. The rheostat base with its associated parts, is thereafter threaded upon said shaft and secured to the back of the support 11 by means of bolts 12. Jumper 25 and contactor 13 are thereafter mounted .upon the shaft and finally the collar 24 is clamped upon the latter in a relation to maintain frictional con-- tact between said contactor and jumper.

The manner of assembly in the relation shown in Fig. 1 will be apparent from the foregoing.

What I claim as new and desire to secure by Letters Patentds:

1. In a reistance control-device, the combination with a helical resistor of a molded insulating base having axially spaced circumferential shoulders forming therebetween a peripheral groove to receive and hold said resistor and having said shoulders upon opposite sides of said groove interrupted at staggered regions.

2. A circular molded insulation base for rheostats and the like having axially spaced helical resistor and having the opposite shoulders interrupted at peripherally spaced and oppositelystaggered regions to facilitate molding of saidbase.

3. A cylindrical molded insulating base having axially spaced series of radially projecting tongues to. provide therebetween a peripheral groove, the tongues of one series being peripherally offset with reference to those of the other series to permit molding of said base under pressure applied at substantially right angles to the plane of said groove.

4. A cylindrical molded insulating base having axially spaced series of radially projecting tongues to provide therebetween a peripheral groove, the peripheral extent of each tongue being-not greater than that of the space between adjacent tongues. and the tongues of one series being offset with reference to those of the other series to bring each tongue into axial register with a space be tween adjacent opposin tongues, whereby said base may be mol ed under pressure applied at substantially right angles to the plane of said groove.

5. A rheostat comprising a cylindrical insulating base having a peripheral groove the opposite walls of which are interrupted at a plurality of diagonally spaced points. a helical resistor stretched within said groove about said base and terminally anchored to the latter, a contactor, an operating shaft. therefor to be journaled in a central axial opening of saidbase, a handle fixed to said sha ftfcollars to be clamped upon said shaft upon opposite sides of said base and contactor sald'base hav ng a countersunk recess .to receive one of said dollars to thereby provide for flat mounting of said base upon a support and for assembling of said base and said handle at will upon the same or upon opposite sides of said support.

- n Witness whereof, I have hereunto subscribed my name.

-' FRANK BOLLER. 

